Embattled Human Services Minister Stuart Robert is set to face more questions about his conduct, as the opposition demands answers to accusations he misused his public office on a trip to China.

The Queensland MP and former assistant defence minister visited Beijing in 2014 and attended a signing ceremony between his friend and Liberal Party donor Paul Marks and Chinese owned company Minmetals.

Federal Labor has called on Prime Minister Malcolm Turnbull to sack Robert if it is proven he breached the ministerial code of conduct, while Shadow Attorney-General Mark Dreyfus has called on Robert to make a statement.

"The Stuart Robert scandal is going to become a test of Malcolm Turnbull's judgement," Shorten told the ABC.

"The writing is on the wall about Stuart Robert. Clearly, the media and Australia are dissatisfied by the information they have so far.

"Malcolm Turnbull has lost more ministers than he's released tax policies for Australia."

Turnbull shouldn't need his department secretary to decide whether Stuart Robert has breached ministerial standards. Show some leadership.